RISK LEVEL ASSESSMENT OF SMALL-SCALE MOUNTAINS STREAM USING A DIGITAL ELEVATION MODEL

In recent years, there has been a tendency toward increased rainfall intensity, and sediment inflow disasters caused by mountain streams are increasing in number. As there is a significantly large number of mountain streams along railway lines, time and effort is spent on local surveys for the purpose of extracting dangerous streams. Additionally, as there is a mixture of diverse factors related to mountain streams, such as terrain, geological features, risk level assessments are differ among technicians. Above all, the risk level assessment of upstream areas located in positions vastly separated from the railway tracks and dispersed over a wide area require a huge amount of time and effort, and there may be a large disparity among engineers. In this paper, therefore, we describe a simple method of evaluating the risk level of mountain stream upstream areas using uniform criteria, without requiring local surveys. In concrete terms, our activity was the development of a scoring sheet that can assess the risk level mainly using the quantitative data of digital evaluation model. It was shown that the evaluation by the scoring table was almost the same as the evaluation by the local surveys.